Field of the Invention
This invention relates to illumination and display technologies, and in particular, it relates to a light-emitting device and related projection system.
Description of the Related Art
Because lasers have the advantages of high brightness and high color purity, they have been widely used in illumination and display technology areas in recent years.
The light distribution of a laser beam is typically an elliptical Gaussian distribution, and the ratio of the major axis to the minor axis is typically large, such as 10:1. In some practical applications, however, the light spot of a light source are required to be a rectangle of a specific aspect ratio. For example, in display technologies, the display screens typically have an aspect ratio of 4:3 or 16:9. Thus, laser beams cannot be directly used as the display light source; light beams from multiple lasers have to be combined using lenses so that the light spots from the multiple lasers are fit together to form a light spot of an aspect ratio of 4:3 or 16:9.
For example, refer to FIGS. 1a and 1b, where FIG. 1a is a plan view of a conventional light source for a projection system, and FIG. 1b illustrates the light spots on the phosphor material in FIG. 1a. As shown in FIGS. 1a and 1b, the conventional light source for the projection system includes multiple laser units 11, multiple collimating lenses 12, a focusing lens 13, a phosphor material 14, a base plate 15, and a motor 16. The base plate 15 is affixed to and driven by the motor. The phosphor material 14 has a ring shape coaxial with the base plate 15 and is disposed directly in contact with it. The laser beams emitted by the laser units 11 are collimated by the corresponding collimating lenses 12 onto the focusing lens 13, and focused by the focusing lens 13 onto the phosphor material 14 to excite the phosphor material 14. The multiple laser units are divided into eight groups, the light spots of all laser units within each group overlap with each other on the phosphor material 14. The laser beams emitted by the eight groups of laser units form eight non-overlapping light spots 17a, which collectively form a predetermined light spot in the rectangular area 17 on the phosphor material 14 (the target plane).
Because multiple light spots are required to be combined to form the predetermined light spot, for each group of laser units, at least one of each laser units 11 and their corresponding collimating lenses 12 need to be adjusted during assembly, to ensure that the light spot formed by each group of laser units 11 on the phosphor material is located at the corresponding predetermined position. This affects the efficiency of assembly and increases assembly cost.